Nitrogen from azomethane

In rats treated subcutaneously with 21 mg/kg C-labelled 1,2-dimethylhydrazine, approximately 13-16% of the radioactivity was released in expired air as CO2 within 24 hours, while 14-15% was expired as azomethane and 17% was released in urine (Fiala et al. 1977). A similar rat study found that the levels of radiolabel in expired CO2 and azomethane after 24 hours were 11% and 14%, respectively, when the dose was 21 mg/kg 1,2-dimethylhydrazine, and 4% and 23%, respectively, when the dose was 200 mg/kg (Fiala et al. 1976). Likewise, rats injected with 20 mg/kg 1,2-dimethylhydrazine expired about 22% of the radioactive dose as azomethane and about 16% as CO2 after 12 hours (Harbach and Swenberg 1981). By quantitating the radioactivity released as azomethane, which contains both nitrogens from the... 

Both symmetrical and unsymmetrical azo compounds can be made, so that a single radical or two different ones may be generated. The energy for the decomposition can be either thermal or photochemical. In the thermal decomposition, it has been established that the temperature at which decomposition occurs depends on the nature of the substituent groups. Azomethane does not decompose to methyl radicals and nitrogen until temperatures above 400°C are reached. Azo compounds that generate relatively stable radicals decompose at much lower temperatures. Azo compounds derived from allyl groups decompose somewhat above 100°C for example ... 

The preparation of compounds containing nitrogen double bonded to another heteroatom has been accomplished by a rDA pathway. Cis- and (rnns-azomethane have been synthesized from tetrahydropyrida-zine (171) by thermal retrodiene extrusion (equation 77). The anti conformation of (171) is presumed to give (rnns-azomethane and the syn conformations yields the cis-isomer. Preparation of nitrosyl hydride (173) has been accomplished under mild nonphotochemical conditions, unlike conditions used in previous preparations. The extrusion of nitrosyl hydride from anthracene adduct (172) as shown in equation (78), which occurs at a very mild temperature, was followed by microwave detection of (173). 

The NN, NO and OO bonds—The interatomic distance between two nitrogen atoms forming a single bond is known from hydrazine in which alternative valence bond structures are not possible, and according to the results of GioufeRE and Schomaker , the value is 1 48 A. The double bond distance N=N in azomethane, GH3—N=N—GHg, is 1 24 A, whereas in diazomethane the bond distance is 1-13 A. 

Structural parameters for some azocompounds reported in the literature from electron or X-ray diffraction studies are collected in Table 1. Trans- and cis-NjFj have planar structures and the carbon-nitrogen skeleton of azomethane is also planar. In N2F2 the cis isomer is 3 kcal.mole" more stable than the trans and in N2H2 the cis isomer is probably also the more stable . In alkyl or aryl substituted derivatives, however, for steric reasons the trans form lies below the cis in energy. The molecular structure of Irons-azobenzene is known to be planar in the solid state while c/j-azobenzene deviates from planarity and a propeller shaped conformation has been proposed, wherein the phenyl rings are rotated approximately 30° out of plane . 

Forst treated the decomposition of azomethane with the quantum harmonic version of the Marcus-Rice theory of unimolecular reactions. He used different models which comprised three dimensional free rotations of the two methyls and of the central nitrogen molecule and adjusted the overall moments of inertia to give the correct total entropy. For planar or tetrahedral methyls calculations gave an increase of six in the number of active rotations in going from the molecule to the complex. With a minimum of assumption it was also possible to reproduce the pressure fall-off curve of the experimental first order rate coefficient for planar and tetrahedral complexes. A further result of the computations is the conclusion that the vibrational frequency pattern of the complex is so much less important than the number of active rotations that both tetrahedral and planar complexes lead to identical fall-off behaviour. 

As part of a study on 1,4-diradicals, various 3,4,5,6-tetrahydropyridazines were decomposed thermally513-518 to olefins and cyclobutane derivatives (see also Section III,G). The activation parameters were measured.519,520 The stereochemical paths of thermal and photochemical nitrogen extrusion from 3,4,5,6-tetrahydropyridazines have been reexamined and rationalized.521 Kinetic measurements of the decomposition of 3,6-dimethyl-3,6-dicyano-3,4,5,6-tetrahydropyridazine have been made.522 Pyridazines with specific functional group orientation can be used as starting material for the preparation of various dienes (Scheme 11). For example, compound 232 is quantitatively transformed into trans,frans-2,4-hexadiene (233), whereas the trans isomer 234 affords exclusively the cis-trans product (235).523,524 1,2-Dimethyl-1,2,3,6-tetrahydropyridazine is thermally decomposed to give mainly trans-azomethane, with about 10% of the cis-isomer.525... 

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